Prehead oven to 350 degrees. Line cookie sheets with sides with foil.
Melt butter in oven on lined cookie sheet. Lay lemon slices on melted butter. Lay shrimp on top of butter and lemons. Sprinkle the dry Italian dressing mix on top of shrimp.
Bake at 350 degrees for 15 minutes, until light golden brown.
This is great alone or served on pasta or rice using melted butter/lemon juice drizzled on top.
It is hard for me to say how many shrimp to use since shrimp come in different weights and sizes. Just use your own judgment. I usually us a medium shrimp and I can lay around 36 on a cookie sheet.